Art of cracking oils



July 23, 1929. E. w. lsoM ART O F CRACKING OILS Filed April l. 1927 2.5K mi 3% 3.8m WKK@ dus x6 thym @RSE Sm BY MMM,

ATToRNE Vl W. ISOM, OF SCARSDLE, NEW YORK, SSIGNOR TO SINCE :t li lc-L COMPANY, OF NEW YORK, N. Y., A CORPORATION OF M l t T OF CRACNG- OILS.

Application tiled April t,

such as gasoline or pressure distillate. The

invention relates particularly to improvements in cracking operations carried out in externally heated, single pass, tubular oil cracking stills. In referring to single pass cracking operations, reference 1s made to cracking operations in which the oil supplied is circulated but once through the oil heating tubes of the still. The invention includes operations in which vaporized fractions-arerefluxed and recirculated through the oil heating tubes, but it is to be distinguished from operations in which the fresh oil itself or any unvaporized portion thereof is recirculated through the heating tubes.

This application is in part a continuation of my prior application filed August 28, 1922,

Serial No. 584,711.

The invention provides animproved method ofA cracking different grades of hy- Adrocarbon oils in which each grade of oil is treated under conditions most advantageous for the cracking of that particular grade of oil andv in which the several operations are combined in such a manner that a greater yield, better quality of product and more eflicient operation may be obtained than it is possible to secure by the separate treatment of the individual grades of oil or a similar treatment of the oil mixture.

In its broader aspect the present invention provides an improved method of cracking hydrocarbon oils in which the oil 1s heated to the cracking temperature in a single pass cracking coil and the hot products therefrom discharged into a body of oil maintained at the cracking ,temperature and in which additional oil, preheated by indirect heat exchange with the, vapors generated during the cracking operation, is introduced directly into the liquid body, only redux condensate free from unvaporized constituents which have been previously subjected to the cracking temperature being permitted to pass through the single pass cracking coil in admixturewith the fresh oil supplied thereto.

The process of the invention is particularly advantageous in connection with the 1927. Serial No. 180,149.

simultaneous treatment of relatively heavy hydrocarbon oils, such as gas oil or fuel oil, and of lighter and more refractory oils, such as kerosene or rerun pressure distillate bottoms.

In the cracking of the more refractory hydrocarbon oils,l for example, kerosene or very light gas oils, it is advantageous to use a hi her temperature to produce the desired crac ing reaction, say to produce gasoline, than 1s commonly used in the treatment of heavier oils, and treatment of the heavier grades of hydrocarbon oils at the temperatures required to crack the more refractory constituents of lighter grades within commercially practicable periods of time results in the formation of excessive quantities of fixed gases and carbon or coke.

In the combined treatment of diderent grades of oil according to the present invention, a Vbody of the heavier oil is maintained at a temperature advantageous for cracking its constituents while the Vmore refractory lighter oil is heated to an advantageous cracking temperature in a singlev pass heating coil and the hot products discharged therefrom intp the body of heavier oil. The heat required t'o maintain the body of heavieroili at the cracking temperature may be supplied entirely lay the heat in the hi h temperature products introduced therein o from the single pass heating coil or this heat may be supplemented by the application of external heat.

At the higher temperatures employed in cracking the more refractory oils it is essential for safety and efiiciency of operation to protect the heating tubes against overheatmg and the formation of carbon deposits therein and at the same time to maintain a .high average temperature diderential' tween the heating gases and the heat ytransferringsurfaces. En the operation of the present invention the deposition of carbon in the heating tubes is-avoided by circulating therethrough only the more refractory oils which do not cause excessive carbon formation at the temperaturesl employed and avoiding the recirculation of unvaporizd loil which has been once subjected to crackperature differential between the heating .gases and the heat transferring surfaces is maintained and excessive local overheating avoided by recirculating a portion of the heating gases which have passed over the heating tubes countercurrent to the ilow of loil therethrough and admixing them with the heated gases contacting with the heating tubes is' increased. The increased vetubes. Thus,

' tures necessary for most ,locity promotes an increase in the rate, and

a more uniform distribution, of the heat absorption throughout the bank of heating the extremely high temperaeiiicient combustion .of the fuel used may be permitted without subjecting the'oil containing tubes to contact with heating gases at excessive temperatures while at the same time a large portion n of the heat contained in the products of comlighter and more bustion is eiiiciently transmitted to the oil being treated. l.

The higher temperature used to crack the refractory hydrocarbon oil tends to promote the formation of fixed gases and unstable, unsaturated compounds, the presence of which are objectionable in the finished product. In the operation of the present invention, however, in which the lighter oils are separately heated to their cracking temperature and subsequently introduced into a body of heavier oil mailitained at the cracking temperature, the unsaturated constituents formed in the first operation apparently tend to react with constituents of the body of hot heavier oil to form more saturated compounds. An increased' yield of constituents suitable as comonents of the desired gasoline or pressure distillate is obtained and the formation of fixed gases and unstable, unsaturated compounds reduced.

`Where the additional fresh oil suiplied to the body of heavy oil isipreheate to substantially the temperature of the liquid body before its introduction thereinto the amount` of heat required to be supplied externally to the liquld body in order to maintain itl at the cracking temperature is materially `reduced-and 1n some casesthe applicationof the latter are permitted to cool appreciably.

external heat to the reservoir may be disused vwith entirely, thereby avoiding any sean er incident to the formation of heat insu ating carbon Adeposits on the heated surfaces of the reservoir.

^' The additional fresh heavy oil introduced to the reservoir may advantageously be passed in countercurrent flow and in indirect eat exchanging relation with the vapors generated in the cracking operation before Thek fresh o il may thus be preheated to a temperature approaching the temperature of the liquid body to which ,it is introduced .and the va ors reiluxed by the cooling effect of the fres oil.V The vapors remaining uncondensed may advantageously be lsubjected to a further refluxing operation in direct contact with a fresh lighter oil and. this further refluxing operation controlled b regulating the 'introduction of the frcs lighter oil thereto so that the desired gasoline product or pressure distillate may be directly produced Ywithoutv subsequent .redistillation. The reiux condensates from both refluxing 'operations together with the fresh lighter oil introduced to the latter reiuxing operation may be returned directly to the single pass heating conduit and additional lighter oil may be independently supplied therewith y.as desired. It will benoted, however, that neither the heavier oil itself nor any of its unvaporzed constituents are ermitted to'pass through the heating con uit with the more refractory constituents.

The invention will be further described in connection with the accompanying. drawings which illustrate, in a diagrammatic and conventionalmanner in elevation and partly in section, an apparatus adapted for the practice of the process of the invention, but it, is intended and will be understood that this i further description and illustration are forv the purpose of exemplification, but the ino0 vof the cracked oil are taken off. The singlepass cracking still or heater comprises a furnace 1 in which a battery of heating tubes 2 are arranged. Oil is forced through the heating tubes by means of a pump .3, entering the heating tubes through connection 4 and, after passing once therethrough, being discharged through connection 5., The heating furnace 1 is provided with a irebox 6 and a stack flue 7,.heating gases being circulated from the firebox ,through the heating furnace over the oil-containing heating tubes therein to the stack flue. The iirebox 6 is provided with means for burning the fuelemployed to supply the heatlzused 1n the cracking operation. A burner for gaseous or liquid fuel is shown at `8. ABefore the hot products of combustion 1n the firebox 6 come in contact with the oil heating tubes 2 in thefurnace 1, they are admixed with a part of the heating gases which have passed over the oil heating tubes and which are returned through connection 9.I The connection 9 is providedwith an inlet 10 adjacent the exit to the stack iue from thev furnace and with an outlet V 11 through which the heating gases withdrawn from near the outlet'of the furnace are returned and admixed with'the hot products of combustion. The return connection 9 includes a blower 12 which may be operated by a steam jet 13 or other sultable means for maintaining circulation of the returned heating ases. g The oil forced through the heating tubes 2 includes fresh oil and constituents refluxed from vapors of the cracked oil discharged from the single pass cracking still or'heater. 1n the apparatus illustrated fresh oil, of a lighter character, is supplied from a receptacle 14 throu h connection 15, and constitu-Y ents refluxedom the vapors of the cracked oil in the reflux towers 21 and 22 together with additional fresh oil introduced to the tower 22 from receptacle 33 by the pump 35 are collected in the receptacle 16 and sup-- plied therefrom through connection 17 to the pump, 3 and forced thereby, together with any fresh oil from the receptacle 14, through the heating tubes 2. rIhe reflux receptacle 16 may be insulated, and the reflux may be returned to the heating tubes at a more or less elevated temperature. The oil discharged from the single-pass cracking still or heater through connection 5 is introduced into the reservoir 18 through pipe 19. Vapors from reservoir 18 escape through connectionf20 to the reflux towers 21 and 22. Uncondensed vapors escaping from reflux tower 22 through connection 23 are discharged to a condenser (not shown) in which the vapors of the cracked oil, forming the desired distillate, are condensed. Pressure in the cracking system may be maintained and regulated by valve24 arranged between the reservoir and reflux towers, or by valve 25 arranged between the reflux towers and the condenser, or by suitable valves arranged beyond the condenser. Fresh oil, of a heavier character, is independently supplied from receptacle 27 to the pump 34 and forced thereby into the body of oil in the reservoir 18 through the reflux tower 21, in indirect heat exchanging relation with the hot vapors therein, by means of the connection 28 and pipe 29. Valved connection 30 provides a by-pass for the fresh oil around the reflux tower 21. A connection 26 is shown for withdrawing tar and fluid residues from the reservoir 18. The unvaporized residue of Aintroduced thereto may be the oil discharged into the reservoir from the single pass tubular cracking still or heater and of the fresh heavier oil independently withdrawn through this connection. During periods when fresh oil is not introduced into the res ervoir, as at the beginning or end of a run, the reflux tower 21 may be cooled by oil circulated from the receptacle 27 through the reflux ltower and discharged through connection 31, or additional cooling oil may' only, by the hot products discharged from'- the single-pass heater, and the connection between the single-pass heater and the reservoir may with advantage be insulated to. prevent heat loss: A

As an example of one particularly advantageous method of operation of the apparatus illustrated in the drawings, in the combined treatment of a heavy gas oil, a light gas oil and a kerosene character distillate, according to the invention, the lightest or kerosene character distillate may be supplied from the receptacle 14 directly to the singlepass 'heating conduit 2 where it is heated -to a temperature of from about 800 to 1200 degrees F. The heavy gas oilmay be supplied from thereceptacle 27 by the pump 34 tothe heat exchanger or reflux tower 21 and from thence to the reservoir 18 through connection 28 and pipe 29. rlhe light gas oil may be supplied from thereceptacle 33 by pump 35 to the reflux tower 22. The body of oil in the reservoir 18v may advantageously be maintained at a temperature of 700 to 850 degrees F. The vapors liberated indthe reservoir 18 pass successively through'the reflux towers21 and 22. The vapors in the reflux tower 22 may be subjected to a refluxing operation in direct contact with the light gas oil introduced thereto from receptacle 33and the light gas oil preheated thereby. rlhe head temperature of the tower 22 may be regulated by the amount of fresh oil supplied thereto, to produce a distillate having the desired end 'pointf All of thetlightest or kerosene character distillate may thus bepass through the single pass heatrequired to mg conduit where it is subjected to the highest temperatures,

and vaporization and escape of the lighter uncracked constituents thereof without being subjected tothe cracking conditions prevented. v

llt is4 apparent thatl various modifications of the process embodying the invention may be made, for example, in the combined treatment of two grades of oil, the heaviery oil may besupplied from the container 27 to the reservo1r 18 while the lighter. oil may be 1ntroduced entirely through the reflux towel' 22 from the receptacle 33 or directly introduced into the heating conduit 2 from the receptacle 14. When possible, however, it is advantageous to regulate the refluxing operation as desired by the introduction of a portion of the lighter oil to the reflux tower 22 and to introduce any excess of the lighter koil, above that required to produce' the desiredrefluxing actlon, directly into the heating conduit. y

I claim:

1. An improved process 'for i cracking -hydrocarbon oils comprising passing a stream of oil once through a heating conlduit and heating it to a cracking temperature therein, discharging the hot products from the heating conduit directly into a body of oil maintained in a reservoir at a cracking temperature, passlng an additional supply ofsfresh oil through a reflux condenser in indirect heat exchanging relation with the vapors generated in the cracking operation to preheat the fresh oil and condense the heavy insufficiently cracked vapors and introducing the fresh oil so preheated directly into the body of oil inthe reservoir, subjecting the uncondensed vapors from the -rst refluxing operation to a further refluxing operation in direct contact with fresh' oil, returning the condensate from both re-Y fluxing operations together with unvaporized fresh oil from said further refluxing operation to the heating conduit, and drawing off unvaporized residual oil from the n reservoir.

2. An improved process for cracking hydrocarbon oils comprising passing a stream of oil once through a heating conduit and heating it to a cracking temperature therein, discharging the hot products from the heating conduit directly into a body of oil maintained in a reservoir at a cracking tem erature, passing an additional supply of resh oil through a reflux condenser in indirect heat exchanging relation with the vapors generated in the cracking operation to preheat the fresh oil and condense' the heavy insulliciently cracked vapors and introducing the fresh oil so preheated directly into the body of oil in the reservoir, subject-y ing the uncondensed vapors from the first refluxing operation to a further reiluxing operation 1n direct contact with fresh oil, introduci-ng the condensate from both reflux- `ing operations together with lunvaporized constituents of the fresh oil introduced to said further reiluxing operation and an additional quantity of fresh oil independently supplied to the heating conduit, and drawing olf unvaporized residual oil from the reservoir.

3. In the cracking of hydrocarbon oils, the improvement comprising passing a stream of light oil once through a heating conduit and heating it to a cracking temperature'therein, discharging the hot products from the heating conduit directly into a body of heavy oil maintained in a reservoir Vat a cracking temperature, passing fresh heavy oil through a reflux condenser in indirect heat exchanging relation with the vapors generated in the cracking operation to preheat the fresh oil and condense the A heavyr insufficiently cracked vapors, introducing the heavy oil so preheated directly into the-body of heavy oil in said reservoir, subjecting the remaining uncondensed vapors Lto a further relluxing operation in direct contact with freshlight oil and returning the condensate from both refluxing operat1ons together with the fresh light oil introduced to said further refluxing operation to the heating conduit.

4. In the cracking of hydrocarbon oils, the improvement comprising passing a stream of light oil once through a heating conduit and heating `it to a cracking temperature therein,

sol

discharging the hot products from the heating conduit directly into a body of heavy oil maintained in a reservoir at a cracking temperature, passing fresh heavy oil through a reflux condenser in indirect heat exchanging` relation with the vapors generated in the cracking operation to preheat the fresh oil and condense the heavinsuliiciently cracked vapors, introducing Vt e heavy oil so preheated directly into the body of heavy oil in said reservoir, subjecting the remaining uncondensed vapors to a further reuxing operation in direct contact With fresh light oil, introducing to the heating conduit the condensate from both refluxing operations, together with the unvaporized portion of the fresh light oil introduced to said4 further refluxing operation and an additional quantity of fresh light oil independently supplied. l

v 5. In the cracking of hydrocarbon oils, the improvement comprising Ypassing a stream of light'oil once through a heating conduit and heating it to a cracking temperature therein, discharging the hot products from the heating conduit directly into a body of heavy oil maintained in a reservoir at a cracking temperature, passing fresh heavy oil through a reflux condenser in in-I direct heat exchanging relation with vapors generated in the cracking operation to preheat the fresh heavy oil and condense the heavy.,insuficiently cracked vapors, intro- ,I

stream of oil once through a heating conduit and heating it to a cracking temperature therein, discharging the hot products from the heating conduit directly into a body of oil maintained in a reservoir at a cracking temperature, passing an additional supply of fresh oil through a reflux condenser inin- 5 direct heat exchanging relation with the vapors generated in the cracking operation to preheat the fresh oil and condense the heavy insufficiently cracked vapors and introducing the fresh oil so preheated directly 10 into the body of oil in the reservoir, subjecting the uncondensed vapors from the first reiuxing operation to a further reiiuxing operation by heat exchange With fresh oil and returning the condensate from both refluxing operations together with fresh oil preheated in said further refiuxing operation to the heating conduit.

In witness whereof, I have subscribed my EDWARD W. IsoM. 

